The purpose of this longitudinal study is to .investigate the impact of maternal substance use (with cocaine as the primary drug of choice) and associated risk factors on toddler self-regulation. Self-regulation in the toddler period is defined by the emergence of impulse control, compliance to directives, and internalization of rules of conduct. Dysregulation in these aspects of toddler functioning may serve as the first step in the trajectory toward increasing regulatory problems in this group of children (e.g. behavior problems, conduct disorder). The study is guided by a developmental psychopathology framework and prior models of development among children of substance using mothers. In this framework, the impact of maternal cocaine use on toddler self-regulation may occur through several pathways. The first is the direct, teratological impact of prenatal cocaine exposure on regulatory processes. The second potential pathway is the impact of maternal cocaine use on growth outcomes, and these in turn influencing infant reactivity and regulation, and toddler self-regulation. A third pathway may be the through the influence of cocaine use on the quality of mother-infant interactionG. A fourth pathway may be the impact of maternal cocaine use on the quality of the care giving environment, defined as exposure to violence, instability in care giving, and maternal psychopathology. Alternatively, these risk factors may moderate the impact of maternal cocaine use on regulation. The protocol involves recruiting mother-infant dyads at birth from two local area hospitals. The final sample will consist of 120 infants prenatally exposed to cocaine and other substances (alcohol, nicotine, and/or marijuana), and 120 non-exposed infants (exposed to no illicit substances or large amounts of alcohol and nicotine). Assessments of physiological (spectral analysis of heart rate and vagal tone) and behavioral reactivity and regulation will be conducted at 1, 7, and 13 months of infant age. Assessments of toddler self-regulation (impulse control, compliance, and internalization) will be conducted at 24 months of age. In addition, mother-infant interactions and the caregiving environment (exposure to violence, care giving instability, and maternal psychopathology) will be assessed at each age. The study will provide information about potential teratogenic effects of cocaine exposure on developmental trajectories to regulatory problems. It will also allow an examination of potential pathways to dysregulation and increase our understanding of risk and protective factors that may moderate regulatory outcomes. Such knowledge may have significant implications for prevention programs designed to ameliorate regulatory disturbances among children of cocaine using mothers.